Dynamic balancers are effective in canceling imbalances in reciprocating engines, and typically include a pair balancer shafts each incorporated with an eccentric mass for counteracting the imbalance in the moving parts of the engine. When the engine accelerates or decelerates, each balancer shaft applies a load to the engine. Particularly in the case of a diesel engine, some rotational fluctuations are inevitable, and this adds to the load of the engine. Furthermore, a diesel engine includes a fuel pump for pressurizing the fuel to a high pressure, and this also applies a fluctuating load to the engine.
The engine disclosed in JP 2004-245131A (patent document 1) uses a gear train, instead of the more conventional timing belt or timing chain, for transmitting the output torque of a crankshaft to balancer shafts and the drive shaft of a fuel pump. However, the various gears are arranged in a highly complex layout, and there is some room for improvement with respect to the optimization of the gear layout. In particular, more compact design and weight reduction are desired.